Abstract It has been suggested that the concentrations of tamoxifen and its demethylated metabolites increase with age. Here, we measured the serum concentrations of the active tamoxifen metabolites, 4OHtamoxifen (4OHtam), 4OHNdesmethyltamoxifen (4OHNDtam, Endoxifen), tamoxifen and its demethylated metabolites. Their relations to age were examined. 151 breast estrogen receptor and/or progesterone receptor positive cancer patients were included. Tamoxifen and its metabolites were measured by liquid chromatography-tandem mass spectrometry. Their serum concentrations were related to the age of the patients. The concentrations of 4OHNDtam, tamoxifen, NDtam (N-desmethyltamoxifen), and NDDtam (N-desdimethyltamoxifen) were positively correlated to age (n = 151, P = 0.017, 0.045, 0.011, and 0.001 respectively). Up to tenfold inter-patient variation in the serum concentrations was observed. The median (inter-patient range) of the concentrations 4OHNDtam in the age groups 30-49, 50-69 and >69 years were 44 (65) ng/ml, 51 (116) ng/ml, and 54 (159) ng/ml, respectively. We conclude that the serum concentrations of 4OHNDtam (endoxifen), tamoxifen and its demethylated metabolites increase with age during steady state tamoxifen treatment. The observed high inter-patient range in serum concentrations of tamoxifen and its metabolites, especially in the highest age group, suggest that use of therapeutic monitoring of tamoxifen and its metabolites is warranted. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-13-13.
Tamoxifen dosage is based on the one-dose-fits-all approach. The anticancer effect of tamoxifen is believed to be due to the metabolites, 4-hydroxytamoxifen (4OHtam), and 4-hydroxy-N-desmethyltamoxifen (4OHNDtam/endoxifen). These demethylated metabolites of tamoxifen have been associated with its side effects, whereas the effect mediated by tamoxifen-N-oxide (tamNox) is still poorly understood. Our objective was to improve the therapeutic index of tamoxifen by personalizing its dosage and maintaining serum tamoxifen metabolite concentrations within a target range. We examined the levels of tamoxifen, 4OHtam, 4OHNDtam, N-desmethyltamoxifen (NDtam), N-desdimethyltamoxifen (NDDtam), and tamNox in serum and in breast tumors specimens of 115 patients treated with 1, 5 or 20 mg/day of tamoxifen for 4 weeks before surgery in a randomized trial. Furthermore, the metabolism of tamNox in MCF-7 breast cancer cells was also studied. The concentrations of tamoxifen and its metabolites in tumor tissues were significantly correlated to their serum levels. Tumor tissue levels were 5–10 times higher than those measured in serum, with the exception of tamNox. In MCF-7 cells, tamNox was converted back to tamoxifen. In contrast to the tissue distribution of tamNox, the concentrations of 4OHtam and 4OHNDtam in tumor tissues corresponded to their serum levels. The results suggest that implementation of therapeutic drug monitoring may improve the therapeutic index of tamoxifen. Furthermore, the tissue distribution of tamNox deviated from that of the other tamoxifen metabolites.
Increased intra-adipose cortisol is thought to promote obesity, but few human studies have investigated intra-adipose glucocorticoid hormones and none have demonstrated prospective changes with fat loss.Subcutaneous adipose tissue (SAT) was obtained from obese subjects before and 1-year after surgery-induced fat loss, and from nonobese controls. In a second similar cohort of obese subjects, adipocytes and stromal-vascular fraction were isolated. Intra-adipose cortisol and cortisone levels were analyzed by liquid chromatography mass spectrometry and HSD11B1/HSD11B2 mRNA by qPCR.SAT cortisol/cortisone ratio before fat loss, median 4.8 (interquartile range, 4.1-5.7), was higher than after fat loss, 1.9 (1.0-2.7) (P = 0.001), and compared to nonobese controls, 3.2 (2.4-3.9) (P = 0.005). Cortisone before fat loss, 2.3 (1.2-2.9) nmol/kg, was lower than after fat loss, 5.8 (3.0-10.2) nmol/kg (P = 0.042), and compared to controls, 5.1 (3.8-6.7) nmol/kg (P = 0.013). HSD11B1 was predominantly expressed in mature adipocytes, whereas HSD11B2 was expressed at a higher level in stromal-vascular fraction.The intra-adipose glucocorticoid metabolism was markedly altered in the extremely obese state with increased cortisol levels relative to cortisone, whereas fat loss restored this balance approximating nonobese subjects. Changes were more pronounced for cortisone than cortisol, suggesting an adaptive response to insufficient intra-adipose cortisol levels in obesity.
Abstract Background Tamoxifen is the most widely used drug for the prevention and treatment of hormone-receptor positive breast cancer (BC). Nevertheless, its clinical effectiveness varies among individuals. Tamoxifen is extensively metabolized by cytochrome P450 (CYP) enzymes, and recent in vivo studies have shown that women with genetically impaired CYP2D6 have reduced production of endoxifen, the main active metabolite. This impairment has been linked to a higher risk of breast cancer recurrence. Despite these observations, the contribution of endoxifen to the overall drug effectiveness of tamoxifen remains uncertain. Methods and results This study presents a pooled analysis of four chemoprevention trials assessing three different low dose tamoxifen schedules: 1mg/day (n=52), 10 mg/week (n=152) and 5 mg/day (n=158). Each participant had signed an informed consent. Genomic DNA was extracted from whole blood by the QIAamp DNA Blood Kit (Qiagen, Valencia, CA, USA), and the CYP2D6 polymorphisms analyzed by the use of the INFINITI CYP450 2D6T Assay (AutoGenomics, Carlsbad, CA, USA). The following alleles were identified: Full enzyme activity: *1, *2; reduced activity: *9, *41 *29; no activity: *3, *4, *5, *6. A total of 336 out of the 362 study participants were genotyped. Circulating concentrations of tamoxifen and its metabolites were determined on cryo-conserved (−80°C) serum samples collected at different treatment intervals according to study design. The women were defined as extensive metabolizers (EM) if they had 2 fully active alleles; intermediate (IM) if they carried reduced alleles or one non-functional allele, while poor metabolizers (PM) carried two non-functional alleles. We found the following phenotype frequencies: 146/336 (43%) EM, 171/336 (51%) IM, 19/336 (6%) PM. When analyzing the effects of phenotypes on serum concentrations of tamoxifen and its metabolites we found a statistically significant effect of phenotype on tamoxifen and metabolites. EM had lower levels of tamoxifen (8,6 ng/mL; P<0.02) and its main metabolite N-desmethyltamoxifen (Ndestam: 17,4 ng/mL; P<0.0001) as compared to impaired metabolizers (IM+PM), who had median tamoxifen levels of 15 ng/mL and Ndestam of 30 ng/mL. No difference was observed on endoxifen levels, possibly due to the low dose schedules. Nevertheless, the increase in Ndestam concentrations in the group of impaired metabolizers is an important indirect effect of lower CYP2D6 activity, showing an accumulation of its main substrate. The relationship between CYP2D6 phenotype and tamoxifen pharmacokinetics will be extended, including women taking tamoxifen at 20mg/day for one year. Conclusions These findings support the relevance of pharmacogenetics in tailoring tamoxifen treatment in the setting of breast cancer prevention. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3675. doi:10.1158/1538-7445.AM2011-3675
IntroductionBreast cancer is the most frequent malignancy and one of the leading causes to cancer related deaths in women.Most human breast cancers express the estrogen receptor (ER) which belongs to the family of nuclear receptors and is a ligand-regulated transcription factor.It is well established that the natural ligand of ER, estrogen, has pro-carcinogenic and growth promoting effects in the mammary epithelium by stimulating proliferation and leaving the cells prone to mutations during cell cycle progression (Foster et al., 2001).Endocrine treatment of hormone sensitive breast cancer targets the estrogen activity in breast cancer cells by blocking the ER with a selective ER modulator (SERM) such as tamoxifen or inhibiting estrogen synthesis using aromatase inhibitors such as anastrozole or letrozole.Endocrine treatment decreases mortality, prolongs disease-free survival and can even reduce the incidence of breast cancer in women at increased risk (Cuzick et al., 2003).Approximately 70 % of women with ER positive tumors respond to endocrine therapy, but resistance do occur, either de novo or develop over time.The molecular mechanism involved in endocrine resistance is one of the central areas of breast cancer research.The trancriptional activity of the ER is not only regulated by its ligands, but also by the level and activity of coregulator proteins.Nuclear receptor coactivators serve as adapters between the receptor and the trancriptional machinery.They possess diverse enzymatic acitivities such as histone acetyltransferase, histone methyltransferase, chromatin remodeling and ubiquitin-conjugation activity and are involved in every step of ER regulated transcription, from chromatin remodeling to transcriptional termination.The members of the p160 family of coactivators are some of the best studied coactivators.These steroid receptor coactivators (SRCs) are small proteins of 160 kDa with similar structural and functional properties, and include SRC-1, SRC-2/transcription intermediary factor-2 (TIF-2) and SRC-3/amplified in breast cancer 1 (AIB1).The SRCs are not only crucial to ER mediated effects in normal tissue.T h e y h a v e a l s o b e e n s h o w n t o b e i n v o l v ed in the carcinogenic process and are www.intechopen.com
Tamoxifen (Tam) has been used experimentally to treat boys with gynecomastia and girls with McCune-Albright syndrome. This drug was recently shown to inhibit the growth of cultured fetal rat metatarsal bones and thus might also affect bone growth in vivo. Four-week-old Sprague-Dawley rats were gavaged daily with vehicle alone (peanut oil), Tam (40 mg/kg/d; 1 or 4 wk), or estradiol (40 microg/kg/d; 4 wk). Five of the 10 rats in each group were killed after 4 wk and the other five after 14 wk of recovery. Bone growth was followed by repeat DXA scans, whereas other bone parameters and spine length were evaluated by pQCT and X-ray at the time of death. Four-week Tam treatment significantly decreased body weight, nose-anus distance, spinal and tibial bone lengths, trabecular BMD, cortical periosteal circumference, and bone strength and also reduced serum IGF-I levels (424 +/- 54 versus 606 +/- 53 ng/ml in control; p < 0.05). Analysis of the tibial growth plate of treated rats showed elevated chondrocyte proliferation (BrdU) and apoptosis (TUNEL), as well as decreases in the number of hypertrophic chondrocytes and in the size of terminal hypertrophic chondrocytes. Despite a complete catch-up of body weight after 14 wk of recovery, the tibia was still shorter (p < 0.001) and its cortical region was smaller. We conclude that, when administered at a clinically relevant dose, Tam causes persistent retardation of longitudinal and cortical radial bone growth in young male rats. Our findings suggest that this inhibition results from local effects on the growth plate cartilage and systemic suppression of IGF-I production. Based on these rat data, we believe that Tam, if given to growing individuals, might compromise cortical bone growth, bone strength, and adult height.
Untargeted proteomics can contribute to composition and authenticity analyses of highly processed mixed food and feed products. Here, we present the setup of an analytical flow tandem mass spectrometry method (AF-HPLC HR-MS) for analysis of insect meal from five different species. Data acquired were compared with previously published data employing spectra matching and standard bottom-up proteomics bioinformatics analyses. In addition, data were screened for insect species marker peptides and common allergens, respectively. The results obtained indicate that the performance of the newly established AF-HPLC HR-MS workflow is in line with previously published methods for insect species differentiation. Data obtained in the present study, also lead to the discovery of novel markers for the development of targeted MS analyses of insect species in food- and feed-mixes and highlighted that known allergen such as arginine kinase or tropomyosin were consistently detected across all five species tested.
